In recent years increased efforts have been focussed on reducing the reliance on fossil fuels as a primary resource for the provision of fuels and commodity chemicals. Carbohydrates and related ‘biomass’ are seen as key renewable resources in the efforts to provide new fuels and alternative routes to desirable chemicals.
In particular, certain carbohydrates can be reacted with hydrogen in the presence of a catalyst system to generate polyols and sugar alcohols. Such processes have been described in Angew. Chemie. Int. Ed. 2012, 51, 3249 and US 2011/313212 and may be used to provide ethylene glycol and 1,2-propylene glycol, which are valuable materials with a multitude of commercial applications, e.g. as heat transfer media, antifreeze, and precursors to polymers, such as PET. Ethylene and 1,2-propylene glycols are traditionally made on an industrial scale by hydrolysis of the corresponding alkylene oxides, which are the oxidation products of ethylene and propylene, produced from fossil fuels.
A major problem encountered in the catalytic conversion of saccharides by known methods is the degradation of the saccharides in reactor feed pipes at high temperatures. Such degradation can lead to fouling and blocking of the pipes. One way to limit this problem is to supply the feed in the pipes at a lower temperature than the degradation temperature of the saccharides. The feed is, therefore, also at a lower temperature than the material in the reactor. However, degradation, fouling and blocking will still occur at the point where the feed pipes enter the reactor, due to the inevitable increase in temperature at this point.
Fouling and blocking of the feed pipes lead to reactor shut-downs for cleaning and/or replacement of the feed pipes and connections. This translates to higher running costs and reduced productivity. It would, therefore, be highly desirable to provide a method to reduce saccharide degradation in reactor feed pipes.